方波脉冲下纳米氧化铝掺杂对聚酰亚胺介电性能的影响

Influences of Nano-alumina on the Dielectric Property of Polyimide Under the Condition of Square Impulses

为了研究方波条件下纳米Al2O3对PI膜介电性能的影响,将粒径为60 nm的Al2O3纳米粒子作为无机填料添加到PI基体中,制作了掺杂量质量分数为1%,2%,5%,7%,10%的PI薄膜。测量了PI/Al2O3薄膜耐电晕性能和介电温度谱以及介电频谱,并用SEM镜观察了放电前后PI/Al2O3薄膜微观形貌。研究结果表明:Al2O3纳米粒子的掺入提高了复合薄膜的耐电晕性能;PI/Al2O3复合薄膜的相对介电常数(εr)与介质损耗正切(tanδ)值随着Al2O3含量升高而升高,其tanδ值随着频率的增加先减小后增大,在200 Hz处有最小值。在同一频率下,PI/Al2O3薄膜εr和tanδ表现出对温度的依赖性,tanδ在70℃与170℃附近出现两个峰值;且随着Al2O3含量的增高,tanδ介电峰向高温方向移动。PI基体中高分子链缠结在纳米粒子周围,纳米粒子所引入的界面以及在聚合物中表现的"钉扎效应"是影响PI/Al2O3复合薄膜介电性能的主要原因。

To study the effect of introducing Al2O3 nanoparticles into PI films on the films＇ dielectric property under square impulses, we tested the dielectric temperature spectra and frequency spectra of PI/Al2O3 films and observed the films＇ microstructure using SEM. The samples were PI films with Al2O3 mass fraction of 1%, 2%, 5%, 7%, and 10%, which were made of PI matrix filled with Al2O3 nanoparticles of 60 nm. The results show that, compared with films of pure PI, the addition of Al2O3 nanoparticles can improve the corona resistance of composite membranes. The permittivity （ε） and dielectric loss （tanδ ofPI/Al2O3 film ascend with increasing particle content of Al2O3, while tanδ decreases with frequency before it starts to increase at 200 Hz. At the same frequency, er and tanδ show a dependency of temperature： tanδ has two peaks around 70 ℃ and 170 ℃, and the peaks move toward higher temperatures in tanδ-temperature plots with the increase of Al2O3 particle content. Further analysis indicates that, in the PI matrix, polymer chains tangling around the nanoparticles, interfaces induced by nanoparticles, and the pinning effects of nanoparticles in polymer are the main reasons of the changes in the PI films＇ dielectric property.